Methods of electrophotographic and electrostatic recording



United States Patent 3,475,170 METHODS OF ELECTROPHOTOGRAPHIC AND ELECTROSTATIC RECORDING Frederick H. Nicoll, Princeton, N.J., assignor to RCA Corporation, a corporation of Delaware No Drawing. Original applicationJan. 14, 1963, Ser. No. 251,062, now Patent No. 3,291,600, dated Dec. 13, 1966. Divided and this application Oct. 5,1966, Ser.

Int. Cl. G03g 13/12 US. Cl. 961.1 14 Claims ABSTRACT OF THE DISCLOSURE This invention relates to electrostatic and electrophotographic printing and more specifically to improved electrostatic and electrophotographic methods of producing visible images. This case is a division of application Ser. No. 251,062, filed Jan. 14, 1963, and now Patent No. 3,- 291,600.

In the art of electrostatic printing, electrostatic images are produced on an insulating surface and are then rendered visible. The electrostatic images may be produced by direct charge deposition as by selectively energizing pin electrodes to deposit charges on an insulating surface in a dot pattern. Images so produced are generally rendered visible by applying thereto electrotroscopic developer particles which are held on the surface by electrostatic forces. This technique of producing and developing electrostatic images is described in greater detail in US. Patent 2,919,- 170 to H. Epstein issued Dec. 29, 1959, and also in US. Patent 2,928,973 to R. W. Crews issued Mar. 15, 1960-. Electrostatic images may also be directly produced on an insulating surface by scanning an electron beam thereover in a vacuum. When the insulating surface comprises the surface of a thermoplastic layer, heat development can be employed to produce a surface-modulated or rippled image which can thereafter be viewed by means of a schlieren optical system. A method for preparing surface modulated tape is described in Thermoplastic Recording by W. E. Glenn, Journal of Applied Physics, volume 30, No. 12, December 1959. Electrostatic images on a photoconductive insulating layer may also be produced by electrophotographic techniques as described in Electrofax Direct ElectrophotographicPrinting on Paper by C. J. Young and H. C. Greig, RCA Review, December 1954, volume XV, No.4.

The foregoing methods of recording are well suited for many practical applications. However, except for the aforementioned thermoplastic recording method, development is generally accomplished with a toner or developer powder. This requires not only means for applying the toner but also means for fixing the toner in place is a permanent image is to be provided. In the thermoplastic recording method described by W. E. Glenn, the thermo- See plastic layer must be maintained in a vacuum during the time the electrostatic image is created thereupon by the electron beam. In addition, the heat developed rippled image often requires a special optical system such as a schlieren system for viewing. With respect to photoconductive layers, selenium and zinc oxide-binder layers, both of which are opaque, have been used. The opacity of such layers has led to complicated procedures for electrophotographically producing transparent slides and films such as, for example, the electrophotographically producing a loose powder image on a photoconductive layer and thereafter electrostatically transferring the powder image to a transparent insulating layer.

Accordingly, it is a general object of this invention to provide improved methods of electrostatic printing for producing visible images.

A further object of this invention is to provide improved electrostatic printing methods for producing projection slides and films. Y

A further object of this invention is to provide improved methods of electrostatic printing which obviate the need for applying developer materials to an electrostatic image.

It is another object of this invention to provide improved methods of producing heat-developed images on an electrostatic printing medium among those which do not require schlieren optics for viewing.

Yet another object of this invention is to provide improved methods of producing heat-developed images on an electrostatic printing medium without the need for vacuum chambers.

In accordance with this invention, many of the foregoing and other objects and advantages are achieved by utilizing a particular type of recording member. Such a member may be prepared by forming a polymeric insulating or photoconductive insulating material into a layer. This material is one which is normally heat-deformable or thermoplastic and which includes molecular chains which can be cross linked when subjected to actinic radiation to render the material substantially non-heat-deformable and insoluble in the polymeric material which has not been so irradiated. Once the layer is formed, an entire recording surface thereon is exposed to actinic radiation to cross link the polymeric material near the surface of the layer to a depth of up to about 500 Angstrom units to thereby form a thin layer, which film is substantially non-' thermoplastic and insoluble in the underlyingthermoplastic polymeric material.

This invention constitutes a method of recording in which one starts with a layer of polymeric insulating material as described above. In one embodiment of this meth- 0d, a film of cross-linked polymeric material is formed on the layer as described. Thereafter, an electrostatic charge pattern is created on the film and it is heated to at least the softening temperature of the thermoplastic polymeric material. Such heating results in a selective breakup of the cross-linked polymeric film coincident with deformation of the underlying thermoplastic material near the interface between it and the film on it. Break-up of the film occurs only in charged areas on the layer and produces a light-scattering image conforming to the charge pattern and having an appearance much like that of frosted glass. Upon cooling, this light-scattering image is frozen on the layer of polymeric material.

In accordance with a second embodiment of this invention, also constituting a method of recording, one again starts with a layer of polymeric insulating material and produces a thin cross-linked film thereon as described heretofore. In this case, however, the polymeric insulating material is one having photoconductive insulating properties and an electrostatic charge pattern or image is produced thereon by electrophotographic techniques, In other respects, the procedures here involved are the same as in the method comprising the first embodiment of this invention.

Another recording method, comprising a third embodiment of this invention, again involves the use of a layer of polymeric insulating material. In this method, the entire recording surface of the layer is not irradiated as before. Instead, the layer is exposed to an image pattern of actinic radiation. When so exposed, a film of cross-linked polymeric material is formed but, instead of covering all the layer, the film is formed only in exposed areas, leaving a thermoplastic surface in all unexposed or masked areas on the layer. After exposure, the entire recording surface is provided with a substantially uniform electrostatic charge. Upon heating to the softening temperature of the non-irridated polymeric material, the crosslinked film in irradiated areas breaks up to again form a light-scattering image.

A fourth embodiment of this invention comprises yet another recording method. In this method, one starts with a special recording member comprising a layer of thermoplastic polymeric insulating material having bonded to one surface thereof a film of relatively non-thermoplastic material which is substantially insoluble in the polymeric material. This film, having a thickness of up to about 500 Angstrom units, may comprise cross-linked polymeric material produced as described in the first embodiment of this invention or it may comprise an entirely dilferent material which has been coated on the surface of the layer. In the instant method, the recording member is exposed to actinic radiation capable of transpiercing the insoluble film on the layer of polymeric material. Exposure is made to a radiation pattern or image and so controlled as to cross link the irradiated polymeric ma terial underlying the insoluble film to a depth of at least 500 Angstrom units. The irradiated polymeric material is thus converted into a high-melting, substantially nonthermoplastic material. Thereafter an overall electrostatic charge is applied to the insoluble film and the layer heated to at least the softening temperature of the non-irradiated polymeric material until the insoluble film covering this material breaks up to produce a light scattering image. Wherever the polymeric material has been actinically cross linked, formation of light-scattering areas is prevented.

RECORDING MEMBERS As mentioned heretofore, recording members used or made for use in this invention include an electrically insulating layer of heat-deformable or thermoplastic material, The layer preferably comprises an organic resinous material capable of undergoing cross linking between molecular chains when subjected to actinic radiation. Among the many such materials having desirable properties, one may cite the following:

(1) Polystyrene (2) Chlorinated parafiins, such as Chlorowax 70,

Diamond Alkali Co., Cleveland, Ohio (3) Polyvinyl chloride (4) Polyvinyl chloride copolymers, such as Vinylite VAGH, VYCM or VMCH (5) Styrene-butadiene copolymers, such as Pliolite 8-5,

The Goodyear Tire and Rubber Co., Akron, Ohio.

(6) Hydrocarbon resins, such as Piccotex 120, Pennsylvania Industrial Chemical Co.

(7) Acrylates and acrylic copolymers, such as Acryloid A101, Rohm and Haas Co., Philadelphia, Pa.

(8) Epoxy base resin which is solid at room temperature such as Epon 1002, Shell Chemical Co., Houston Texas (9) Thermoplastic hydrocarbon terpene resins, such as Piccolyte 8-135, Pennsylvania Industrial Chemical Co.

Various combinations of resinous materials can be employed to modify the physical properties of the insulating layers such as the softening point or flexibility thereof. Other materials may be added to modify the physical properties of the layers, provided they do not interfere with the electrical properties thereof. For example, various plasticizers may be added to enhance flexibility of the layers or to enhance formation of a thermoplastic material into a layer.

The recording members preferably also include a suitable support element for a thermoplastic layer. These include metal plates, glass plates, glass slides coated with conductive tin oxide, high-melting films such as Mylar or Cronar which have been coated with copper or aluminum, and high-melting conductive plastics.

Example I A solution is prepared comprising 20% by weight of polystyrene dissolved in toluene. This solution is poured onto a lantern slide coated with conductive tin oxide. The slide is allowed to drain for about one minute and is dried on a hot plate for about /2 minute at C.

The entire exposed surface of the polystyrene layer, so produced on the slide, is then subjected to actinic radiation to cross link the polystyrene to a depth of up to about 500 Angstrom units, the cross-linked polystyrene thus comprising an insoluble thin film adhering to a layer of thermoplastic noncross-linked polystyrene.

A thin cross-linked film can be produced on a polystyrene layer by subjecting it to many kinds of actinic radiation, For example, the layer can be exposed to short wavelength ultraviolet light. Specifically, an excellent film can be produced with an exposure of about 5 seconds 4; inch from a source-emitting ultraviolet, a portion of which has a Wavelength about 2000 Angstrom units.

Electron bombardment will also produce an appropriate cross-linked film. It has been found that best results are achieved by electron bombardment with a voltage of about 2000 volts and about 10- coulombs per square centimeter. If the voltage is too high, excessive penetration of the beam will result in cross linking the polystyrene to too great a depth, i.e. more than about 500 Angstrom units. An adequate film of cross-linked polystyrene having the desired thickness can also be produced by exposure for less than 30 minutes, 10 inches from a 20 milliamp, 45,000 volt tungsten-target X-ray source through a beryllium window. Here again, if the X-rays penetrate too deeply or are too hard, to deep a film of the polystyrene will be cross linked.

' A lantern slide prepared as above has a surface film of cross-linked polystyrene, less than 500 Angstrom units in thickness, overlying and adhering to a heat-deformable layer of polystyrene, 19 microns or less in thickness, on the conductive coating on the glass slide.

ELECTROSTATIC RECORDING Some embodiments of this invention envisage including the step of producing a thin cross-linked film on a polymeric layer as part of continuous recording or printing processes. For example, having been provided with a lantern slide coated with a thermoplastic polystyrene, such as that of Example I, the first step in such a process constitutes the production of a thin cross-linked film on the slide in the same manner as'described in connection with Example I. Thereafter a suitable mask or stencil is superimposed on the coated surface of the slide and it is subjected to a corona discharge to' produce an electrostatic image on the coated surface in those areas which are not masked by the stencil. Having produced a charge pattern on the coated slide, it is then heated to a temperature sufficient to soften the polystyrene layer under the crosslinked polystyrene film, whereupon a surface deformation results in the areas of the charge pattern to form a clearly visible light scattering image which, upon cooling, is fr0zen in place.

In the method of the immediately preceding paragraph, the charge pattern can be readily produced by passing over the masked slide two or three times a corona-generating unit consisting of one or more fine wires, 2 to 3 mils in diameter, maintained at a potential of from 4,000 to 7,000 volts while supplying a ground connection to the tin oxide coating on the slide. Heat development can be easily accomplished by contacting theuncoated side of the slide to a hot plate maintained at about 140 C. until the surface deformations are seen to form. These deformations, which have the appearance of frosted glass, will form in about 9 seconds or less. With the 'hot plate at 215 C., heat development can be accomplished in about one second.

In this method and in others to be described hereinafter, the thicknesses of the polystyrene layer and of the crosslinked film play important roles. If a polystyrene layer of about 11 microns or less is employed, an interference pattern may be heat-developedon the coated slide. For example, an image produced on a slide which has a polystyrene layer about 1 micron thick will result in surface deformations which scatter light which is predominantly blue in color. Slightly thicker layers will result in scattering of green and red light.

For best results in the instant invention, the cross-linked film on the polystyrene should not exceed about 100 A. in thickness. Light-scattering patterns can be produced with cross-linked films as thick as 500-1000 A. but only with a corresponding decrease in surface deformation and image contrast. Accordingly, it is generally preferred that the cross-linked film have a thickness of from 5 0 to 100 A.

In lieu of the stencilling method for producing electrostatic charge patterns on a coated slide, as described heretofore, such charge patterns may be produced by direct deposition of charges in patterns as described in either US. Patent 2,919,170 to Epstein or 2,928,973 to Crews mentioned above, or by electron beam scanning as described in the W. E. Glenn publication or in the W. E. Glenn Patent 3,008,006. However the charge pattern may be produced, heat development will form a visible light-scattering image on the coated surface of the slide.

ELECTROPHOTOGRAPHY A visible light-scattering image may also be produced on the coated slide of Example I by. a method which is based on the photoconductivity of polystyrene. Although polystyrene is not normally considered as a photoconductive materal, when employed in thin layers as are specified herein, it exhibits a photoconductive response when eX- posed to intense ultraviolet light. Thus, in this method, the first step again comprises actinic irradiation of the polystyrene to produce a thin cross-linked film thereon. A substantially uniform electrostatic charge is then applied to the entire coated surface of the slide as by means of a corona-generating unit. It is then exposed to an intense pattern of ultraviolet light. Such exposure can be accomplished in a few'rninutes with light from an arc lamp passing through a suitable mask. Wherever light has struck the coating, the electrostatic charge is dissipated, leaving a charge image thereon corresponding to the masked areas. This charge image is then heat-developed as described heretofore to produce a positive light-scattering image.

Slides prepared as described herein may be viewed in an ordinary slide projector. The dark areas of the projected image correspond to the developed or light-scattering areas produced on the slide. Such slides may also be viewed by schlieren projection, in which case the bright areas of the projected image will correspond to the lightscattering areas on the slide.

The foregoing electrophotographic method, while satisfactory for many purposes, has limited applicability because the photoconductive response of the polystyrene layer is essentially limited to relatively short wavelength ultraviolet light. Response to ultraviolet light of longer wavelengths can be enhanced with a polymeric layer produced as follows:

Example II A coating solution is prepared which consists of:

13.9 grams polystyrene solution (36% by weight solids in toluene) 3.0 grams of the dye intermediate bis (4,4'-ethylbenzylamino-phenyl) phenyl methane, having this formula:

The latter material is dissolved in the polystyrene solution diluted with about 17 grams of toluene and a conductively coated slide is overcoated therewith to provide there on a photoconductive layer.

A cross-linked film is produced on the slide by actinic radiation as in Example I. The coated slide is then subjected to corona discharge to provide a substantially uniform electrostatic charge on the coating thereon. It is then exposed to light passing through a photographic transparency. Exposure using two 4-watt black lamps (ultraviolet) held at about 4" from the slide for about 10 seconds or less will produce a latent electrostatic image on the slide. A visible light-scattering image is produced thereon in about one second by contacting the uncoated side of the slide to a hot plate at 215 C.

Preferred recording members include photoconductive layers sensitive to light well above the wavelength of ultraviolet. Such layers may be prepared using resins such as those listed heretofore or combinations of such resins and dissolving a suitable dye intermediate therein. 40 The resin not only acts as a binder for but also reacts with the dye intermediate to form a third material which acts as a photoconductive sensitizer. The sensitizer may be a dye formed from the dye intermediate. In many cases, less than one percent of the dye intermediate need be converted to the sensitizer to provide maximum sensitivity to photoconductive layer. Formation of more sensitizer merely increases the amount of color in the layer without any appreciable increase in photoconductive sensitivity. With only trace amounts of sensitizer needed and with dye intermediates and resinous materials, photoconductive layers can be prepared which are substantially transparent to light within the visible spectrum, which have a resistivity in darkness of at least 10 ohm centimeters, and which have a resistivity of at least two orders of magnitude (10 less when irradiated.

A substantially transparent recording element which includes a photoconductive layer having a high value of photoconductive sensitivity may be prepared as follows:

Example III (b) a second solution is prepared by dissolving: 4 grams chlorinated paraflin (Chlorowax and 2 grams bis-(4,4'-dimethylamino-phenyl) phenyl methane (same formula as that just above) in 20 grams methyl ethyl ketone 10 grams of solution (a) and 5 grams of solution (b) are then mixed together to form a coating solution.

A special slide is prepared for coating. This slide, having a thin conductive tin oxide layer on one surface, is provided with an additional layer of metal such as nickel or gold by means of vacuum evaporation. Nickel, for example, is evaporated onto the tin oxide layer to a thickness which provides a coating having a resistance of from about 35 to about 110 ohms per square. Contact to the nickel coating is provided for by applying thin strips of conducting silver paint along opposite edges of the nickel layer. The nickel and tin oxide layers are sufficiently thin so as not to detrimentally affect the use of such slides for optical projection. This specially prepared slide is'then flow-coated with the aforementioned coating solution to provide thereon, when dried, a photoconductive layer with a thickness of about 25 to 50 microns.

A crosslinked film is produced on the photoconductive coating by actinic radiation as in Example I. The slide is then charged and exposed to a projected image. Exposure is conveniently accomplished with a tungsten lamp using, for example, 15,000 foot candle seconds illumination. A light-scattering image is then obtained by passing current through the nickel film to heat develop the slide. Heat development can be accomplished in as little as of one second with from about 6 to 17 Watt seconds of heating.

There are many dye intermediates, other than those specifically set forth in Examples II and III, which can be used in the photoconductive layers described herein. In general, suitable dye intermediates which are soluble in suitable thermoplastic resinous materials are selected. Preferred dye intermediates have the general formula:

wherein R and R are selected from the class consisting of monoalkylamino, di-alkylamino, mono-arylamino and alkylarylamino; X is selected from the class consisting of wherein R is selected from the class consisting of H, OH, CH3, OCH3, R1 and 8 (2) Bis (4,4 dimethylaminophenyl) 4" -methoxyphenyl methane.

CH H CH (3) Bis (4,4' dimethylaminophenyl) -,4" hydroxyphenyl methane.

CH5 CH3 N CH3 H CH3 (7) Bis (4,4" dimethylaminophenyl) 2",4" dihydroxyphenyl CH3 v 1 1 (8) Tris- (4,4',4"-penylaminophenyl)methane.

1 1 (22) tris-(4,4'4"-ethylphenylaminophenyl)methane.

ACTINIC RADIATION RECORDING The present invention includes novel. methods of electrostatic printing other than as previously described. These methods include the steps of exposing a heat-deformable polymeric coating, such as polystyrene, to an image pattern of actinic radiation to create, in the exposed areas, a latent image comprising cross-linked polymeric material. After exposure, a uniform over all electrostatic charge is produced on the coating and it is then heated to at least the softening temperature of the noncross-linked polymeric coating material. This procedure produces a light-scattering image in the same manner as described heretofore.

In one of these methods, cross linking is accomplished in the same manner as described with respect to Example I, for example, by exposure to ultraviolet, electron bombardment, X-ray or other suitable actinic radiation. However, instead of subjecting the entire surface of the polystyrene coating to actinic radiation, as in Example I, exposure is accomplished in image configuration. For example, a mask, stencil or photographic transparency can be superimposed on the coating and exposure made therethrough so that a cross-linked film is produced on the coating only in those areas under the open or transparent areas of the mask. Exposure may be accomplished in a similar manner with X-ray or electron bombardment. As an alternative, imagewise exposure may be accomplished by scanning an electron beam over the surface of the coating. However exposure in accomplished, a light-scattering image is produced by uniformly charging and heat developing the coating in the same manner as described heretofore.

In another of these methods, one starts with a record* ing member which includes a layer of thermoplastic polymeric material coated with a thin film of insoluble material. The film may comprise cross-linked polymeric material as in Example I or it may comprise a different material. An example of the latter type is prepared as follows:

EXAMPLE IV A solution is prepared comprising 20% by Weight of polystyrene dissolved in toluene. This solution is poured onto a lantern slide coated with conductive tin oxide. The slide is allowed to drain for about one minute and is dried on a hot plate for about /2 minute at 140 C. Suitable thermoplastic materials may be substituted herein for the polystyrene in the same way as in Example I. The sensitivity of the polystyrene to actinic radiation can be enhanced by including therein a dye intermediate in the same manner as in Example II.

After coating, as above, the slide is immersed in a water solution containing about 0.02% by weight of polyvinyl alcohol. The lantern slide is then fiushed with deionized water and briefly heated on the hot plate until dry. A lantern slide prepared in this manner has a surface film of polyvinyl alcohol less than Angstrom units in thickness overlying a polystyrene layer of about 19 microns or slightly less in thickness adhering to the tin oxide coating on the lantern slide.

One method by which a visible, light-scattering image can be produced on the slide of Example I or Example IV is by superimposing thereon a mask, stencil or photographic transparency and then subjecting the coated surface of the slide to actinic radiation from an ultraviolet source. Such a source may comprise, for example, a commercially available low pressure mercury vapor resonance germicidal lamp. When the slide is exposed through a mask to such a lamp (8 watt) at a distance of about inch the ultraviolet light will penetrate the thin film on the slide and cross link the underlying polystyrene layer atleast to the minimum depth of about 500 A. in about 1 minutes. Crosslinking time can be considerably reduced by exposure to the more intense light of an arch lamp.

After exposure, a corona-generating unit is passed over the polyvinyl alcohol film on the slide to provide an overall electrostatic charge on the film. A suitable coronagenerating unit may comprise one or more fine wires, 2 to 3 mils in diameter, maintained at a potential of from about 5,000 to 9,000 volts.

Having produced a substantially uniform electrostatic charge on the coated slide, it is then heated to a temperature sufficient to soften those portions of the polystyrene layer which have not been exposed to and cross linked by actinic radiation. When so heated, the polyvinyl alcohol film overlying the softened portions of the polystyrene breaks up and distorts the surface of the coated slide to produce a light-scattering image thereon much like that of frosted glass. Heat development of a light-scattering image can be readily accomplished by contacting the uncoated side of the slide to a hot plate maintained at about 140 C. until the light-scattering or frosted image is seen to form. This will occur in about 9 seconds or less. With the hot plate at 215 0., heat development can be accomplished in about one second. Wherever actinic radiation has penetrated the polyvinyl alcohol film to cross link or harden the underlying polystyrene, no light-scattering effect is produced.

As mentioned heretofore, actinic radiation other than ultraviolet may be used during the exposure step to produce cross linking in the polystyrene layer. These include electron bombardment, X-ray or alpha particle bombardment and others. For example, the polystyrene layer can be cross linked to more than the minimum required depth by exposure to a 5,000 volt (or more electron beam using about 10'" coulombs per square centimeter. Adequate cross linking can also be obtained by exposure for about one-half hour at 10 inches to a 20 milliampere 45,000 volt tungsten-target X-ray source.

Light-scattering images can be produced on the slides of the following examples in the same manner as described with respect to the slide of Example IV. With the addition of a suitable dye intermediate, sensitivity to actinic radiation can be enhanced.

EXAMPLE V A conductive glass slide is coated with a layer of polystyrene as in Example I. The coated slide is then immersed in a solution of 1 part by weight of gelatin in 10 parts water and is then flushed with distilled water and dried.

EXAMPLE VI A solution is prepared comprising 2.5% by weight of a thermoplastic hydrocarbon resin (Piccotex in tol- 13 uene. As in Example IV a conductive glass slide is coated with this solution and a thin film of polyvinyl alcohol.

EXAMPLE VII EXAMPLE VI II A lantern slide is prepared with a polystyrene coating (Example I) which, when dry, is overcoated with a gold deposit having a mean thickness of about0.4 A. Such overcoating is conveniently accomplished by means of well known vacuum evaporation or sputtering techniques.

EXAMPLE IX A lantern slide is prepared with a thermoplastic resin coating as in Example N which is overcoated with an aluminum oxide deposit having a mean thickness of about 0.4 A. 'Overcoating is accomplished by vacuum evaporation of aluminum onto thte resin coating. Upon exposure to air the aluminum becomes converted to aluminum oxide.

What is claimed is:

1. A method of recording on a member including a layer of heat-deformable polymeric insulating material capable of being rendered substantially non-heat deformable when subjected to actinic radiation; said method comprising the steps of:

actinically irradiating to a depth of up to about 500 Angstrom units and electrostatically charging said layer, at least one of said irradiating and charging steps being carried out in conformity with an image pattern; and

heating said layer to at least the softening temperature of said heat-deformable material to produce a light-scattering image on said layer in areas subjected to the combined effect of said irradiating and charging steps.

2. A method of recording on a layer of heat-deformable polymeric insulating material capable of being rendered substantially non-heat deformable when subjected to actinic radiation; said method comprising the steps of:

uniformly exposing a surface of said layer to actinic radiation to produce a substantially non-heat-deformable film thereon having a thickness of up to about 500 Angstrom units;

establishing an electrostatic charge pattern on said layer; and

heating said layer to at least the softening temperature of said heat-deformable polymeric material to produce a light-scattering image on said layer in areas conforming to the electrostatic charge pattern. 3. A method according to claim 2 in which said layer is also photoconductive and said charge pattern is established electrophotographically.

4. The method of claim 3 wherein said charge pattern is produced by establishing an overall electrostatic charge on said layer and exposing said layer to a light image. 5. A method of recording on a layer of heat-deformable polymeric insulating material capable of being rendered substantially non-heat deformable when subjected to actinic radiation, said method comprising the steps of: exposing a surface of said layer to an image pattern of actinic radiation to produce in exposed areas thereon a film of non-heat-deformable material having a thickness of up to about 500 Angstrom units;

establishing an overall electrostatic charge on said layer; and

heating said layer to at least the softening temperature of said heat-deformable material to produce a lightscattering image on the irradiated portion of said layer.

6. A method of recording on a layer of heat-deformable polymeric insulating material capable of being rendered substantially non-heat deformable when subjected to actinic radiation, said method comprising the steps of:

actinically irradiating substantially an entire surface of said layer to produce a substantially non-heat-deformable film thereon having a thickness of up to about 500 Angstrom units;

exposing said surface to an image pattern of actinic radiation capable of transpiercing said film to render the polymeric material underlying said film in exposed areas substantially non-heat deformable to a depth of at least 500 Angstrom units;

establishing an overall electrostatic charge on said layer; and

heating said layer to at least the softening temperature of said heat deformable material to produce a lightscattering image on those portions of said layer subjected to said image pattern of actinic radiation.

7. A method of recording on a layer of heat-deformable polymeric insulating material capable of being rendered substantially non-heat deformable when subjected to actinic radiation; said method comprising the steps of:

subjecting said layer to an image pattern of said actinic radiation to produce a substantially non-heatdeformable film in pattern form having a thickness of up to about 500 Angstrom units;

producing an electric field across said layer by exposing said recording element to a corona-generating source;

heating said layer at least to the softening temperature of said heat-deformable polymeric material to produce a light scattering image on those portions of said layer subjected to the combined efiect of actinic radiation and said electric field; and

allowing said layer to cool and freeze said light-scattering image to form a recorded image pattern.

8. A method of recording on a recording member comprising a layer of heat-deformable polymeric insulating material capable of being rendered substantially nonheat deformable when subjected to actinic radiation and an adherent film of material which is insoluble in said polymeric material, said film having a maximum thickness of about 500 Angstrom units; said method comprising the steps of:

exposing said recording member to an image pattern of said actinic radiation to produce a latent image pattern of non-heat-deformable polymeric material to a depth of at least about 500 Angstrom units under said film;

producing an overall electrostatic charge on said layer; and

developing a visible image on said recording member by heating said layer to at least the softening temperature of said heat-deformable material to cause said film to break up and distort said heat deformable material to produce a light-scattering image on said recording member where said layer has been subjected to both irradiation and charging.

9. A method according to claim 8 in which said radiation is ultra-violet radiation.

10. A method according to claim 8 in which said radiation is applied by electron bombardment.

11. A method according to claim 8 in which said radiation is X-ray radiation.

12. A method of electrostatic printing using a recording element comprising a layer of insulating, normally thermoplastic polymeric material capable of being rendered substantially non-thermoplastic when subjected to actinic radiation; said method comprising the steps of:

producing a latent image on one surface of said layer by controllably exposing said surface to an image 14. The method of claim 12 wherein said surface of of said actinic radiation to produce in image areas said layer is controllably exposed by bombarding selected thereof a substantially non-thermoplastic adherent areas of said surface with electrons. film having a maximum thickenss of about 500 Ang- I strom i 5 References Cited producing at least on the image areas of said record- UNITED STATES PATENTS ing element an electrostatic charge; and heating said recording element to soften said polymeric 2 39 et material and cause said film to break up and dis'-' 7 0 6 96-11 tort the surface of the underlying polymeric material 10 GEORGE E LESMES, Primary Examiner to create a light-scattering image recordmg element Where said layer has been both irradiated and VAN HORN, Assistant Examiner charged. 1 13. The method of claim 12 wherein said surface of said layer is controllably exposed to an image pattern 5 17 340 1'73; 355 '9' of ultra-violet light.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,475,170 Dated tObeI 28, 1969 Inventor(s) Frederick H. Nicoll It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 9, structural formula 11, should read as follows:

OCH3 NO? O CH3 H CH3 Column 10, structural formula 15, should read as follows:

OCH3

Column 13, line 9, change "1969" to 1960 SIGNED AND SEALED M 1 21978 (SEAL Attest:

EdWardMFIctnheqIr. mm B. SGHUYLER, IR.

Attesting Omar comllllioner of Patents 

